terblance 2.qxd 2005/12/09 10:31 Page 73 The vegetation of three localities of the threatened butterfly species Chrysoritis aureus (Lepidoptera: Lycaenidae) R.F. TERBLANCHE, T.L. MORGENTHAL and S.S. CILLIERS Terblanche, R.F., T.L. Morgenthal and S.S. Cilliers. 2003. The vegetation of three local- ities of the threatened butterfly species Chrysoritis aureus (Lepidoptera: Lycaenidae). Koedoe 46(1): 73–90. Pretoria. ISSN 0075-6458. The vegetation and habitat characteristics of three localities of Chrysoritis aureus at the Alice Glockner Nature Reserve, Suikerbosrand Nature Reserve and Malanskraal farm near Heidelberg in South Africa, were compared. A numerical classification technique, TWINSPAN, was used and refined by using Braun Blanquet procedures to classify the vegetation at the different localities. A DCA ordination was applied to confirm the results of the classification. Although the general vegetation structure at the three habi- tats of Chrysoritis aureus were found to be similar, marked differences in the floristic composition were evidenced. A different sub-community, compared to the vegetation at Suikerbosrand and Alice Glockner Nature Reserve, was recorded at the Malanskraal habitat of Chrysoritis aureus. These differences in floristic composition, but with simi- larities in vegetation structure, indicate the possible importance of fire for the ultimate survival of these butterflies in the Rocky Highveld Grassland. The host plant of Chrysoritis aureus, Clutia pulchella, collected at Malanskraal differed markedly and consistently in their morphology, compared to the individuals from the habitats at Suikerbosrand and Alice Glockner Nature Reserve. These differences in the floristic composition of one of the habitats compared to the others, raise research questions con- cerning the butterfly metapopulation structure, since the subpopulations seem to be adapted to slightly different habitat conditions. The variation in the habitat suggests that the “last remaining locality scenario” for other localised butterflies in South Africa, such as Orachrysops niobe, needs to be redressed. Management strategies are addressed while the importance of conserving rare, localised ecosystems are highlighted by the phytosociological study. Key words: myrmecophilous, Lycaenidae, Chrysoritis, Clutia, Crematogaster, habitat, phytosociology, conservation R.F. Terblanche ([email protected]), T.L. Morgenthal & S.S. Cilliers, School of Environmental Sciences and Development, Private Bag X6001, Potchefstroom Univer- sity for CHE, Potchefstroom, 2520 Republic of South Africa. Introduction tower near the Natal road of Heidelberg in Gauteng (Pringle et al. 1994). During 1983, The butterfly Chrysoritis aureus—previously Chrysoritis aureus was added to the protect- known as Poecilmitis aureus before the new ed wild animal list of the former Transvaal combination was designated by Heath (1997) under Ordinance 12, since the type locality —is considered to be Rare in the Red Data had been the only known area where the but- book of butterflies (Henning & Henning terfly ocurred (De Wet 1987). G.A. Henning 1989) and the updated list of the Red Data found another locality near Greylingstad book of butterfly species (Henning & Hen- (Pringle et al. 1994). Members of the Lepi- ning 1995). C.R. Barrett and F. Coetzee dis- dopterists’ Society of Africa found another covered Chrysoritis aureus on Christmas locality in Suikerbosrand Nature Reserve Day 1959 on a rocky slope below the water (Henning & Henning 1989) after teams of ISSN 0075-6458 73 Koedoe 46/1 (2003) terblance 2.qxd 2005/12/09 10:31 Page 74 Fig. 1 The location of the habitats of Chrysoritis aureus that were studied. lepidopterists carried out organised exten- limited to the north eastern extreme of the sive exploration in this reserve (Fig. 1). The reserve, even though the Lepidopterists’s colony at Suikerbosrand seems to be limited Society of Africa organised surveys that cov- in numbers (Henning & Henning 1989; Roos ered many different habitats in the reserve & Henning 2000) though the numbers tend (G.A. Henning 1986a, 1986b, 1987). After to remain stable (The word ‘colony’ refers to decades of exploring by a number of lepi- the subpopulations of these butterflies, that dopterists in the hilly areas of Gauteng and is where they actually breed. The adults usu- the adjacent Mpumalanga (Table 1), only ally also fly at or close to these restricted five confirmed localities of Chrysoritis areas). In the Suikerbosrand Nature Reserve, aureus were reported. The distribution of the the only recorded habitat of the butterfly is butterfly can be described as patchy and Table 1 The locality, altitude and geological system present at the confirmed localities of Chrysoritis aureus Locality Province Locality *Altitude (m)Geological Supergroup Alice Glockner NR 8 km S Heidelberg Gauteng 26º34'S, 28º22'E(2628CB) 1690 Witwatersrand Hill N of Greylingstad Mpumalanga 26º44'S, 28º44'E(2628DA) 1810 Ventersdorp Malanskraal locality 14 km W Balfour Mpumalanga 26º39'S, 28º26'E(2628CB) 1780 Ventersdorp Suikerbosrand NR Gauteng 26º29'S, 28º18'E(2628AD) 1720 Witwatersrand Type locality at Heidelberg Gauteng 26º29'S, 28º21'E(2628AD) 1600 Witwatersrand * The grid reference reading is from the north western corner of each minute by minute square. **The Malanskraal locality is close to the borderline between the Ventersdorp supergroup and the Witwatersrand Supergroup. Koedoe 46/1 (2003) 74 ISSN 0075-6458 terblance 2.qxd 2005/12/09 10:31 Page 75 Chrysoritis aureus is very localised at each of these localities. The three habitats studied each cover approximately 200 m² – 400 m². All the recorded localities of Chrysoritis aureus are situated at sites where formal or informal urban development pose an ever- increasing threat to the habitat. Habitat destruction across the world as the main cause for the extinction of populations of localised butterflies, is well recognised, thereby emphasising the primary importance of habitat conservation (S.F. Henning 1987; Larsen 1995; Kudrna 1995; Munguira 1995; New 1995; Oates 1995; Opler 1995; Pullin et al. 1995; Thomas 1995; Warren 1995). An ongoing comparative study of the Chrysori- tis aureus habitats (vegetation) is therefore imperative to gain knowledge for develop- ing strategies for the conservation of these habitats. A description of the vegetation of the Chrysoritis aureus habitats is needed if management practices such as translocation of butterflies or habitat restoration is consid- Fig. 2. Clutia pulchella ("Heidelberg morpho- ered. Vegetation studies of the habitats of the type"), the host plant of Chrysoritis aureus. threatened Golden Sun Moth in Australia (O’Dwyer & Attiwill 2000), provided essen- tial information for the restoration of its habitat. A vegetation analysis of the then only known habitat of a threatened butterfly, Aloeides dentatis subsp. dentatis, in South 1993; Retief & Herman 1997) (Fig. 2). The Africa, (Deutschländer & Bredenkamp larvae of Chrysoritis aureus are also con- 1999) was very applicable for its conserva- stantly tended by ants of the genus Cremato- tion management. For this study, the vegeta- gaster (Henning 1983). During the day, the tion of three habitats were compared to iden- larvae shelter for protection and only appear tify possible key factors and to detect possi- at night to feed on their host plants (Henning ble differences between these habitats. 1987a). Well developed dorsal nectary This study also forms part of an ongoing organs (Cottrell 1984) or honey glands (Hen- investigation into the reasons why the sub- ning 1983; 1987a) are present on the larvae populations of the butterfly are confined to and the ants are attracted to feed on the secre- such small areas. In South Africa, studies on tions of these organs (Henning 1983, 1987a). myrmecophilous butterflies, such as In the absence of the ants, a fungal infection Chrysoritis aureus, are limited to life histo- occurs in the dorsal nectary organ and the ry descriptions or reporting of information on the host plant and host ant. Some clues larvae often die after a few days (Henning for the confinement of Chrysoritis aureus to 1983) (Fig. 3). Since both the ant and the its habitats can be found in its life history host plant are needed for survival of (Henning 1983). The host plant of the larvae Chrysoritis aureus at any locality, the habitat is the small shrub Clutia pulchella L. Sens. requirements are complicated. These include lat. (Euphorbiaceae) which is widely distrib- specific local vegetation communities. We uted in South Africa (Arnold & De Wet therefore investigated the vegetation, to con- ISSN 0075-6458 75 Koedoe 46/1 (2003) terblance 2.qxd 2005/12/09 10:31 Page 76 frosty winters. According to information obtained from the South African Weather Service, the long-term average annual rain- fall data from nearby weather stations vary considerably between 620-750 mm per annum (South African Weather Service, Pri- vate Bag X097, Pretoria, 0001). Variation in topography, the rock cover and vegetation structure results in different meso- and microclimates. The sites that were investigated are situated in the Grassland Biome (Rutherford & Westfall 1994; Low & Rebelo 1996), the Bankenveld (Acocks 1988) or Rocky High- veld Grassland (Bredenkamp & Van Rooyen 1996). Fig. 3. The larva of Chrysoritis aureus. The two white structures at the anterior Materials and methods (head) area, are tubercle organs. Note the fungal growth at the posterior end at Sample plots (5 m x 5 m) were placed